[Python-ideas] csv.DictReader could handle headers more intelligently. (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Thu Jan 24 13:38:58 CET 2013

Le Thu, 24 Jan 2013 22:33:07 +1000, Nick Coghlan <ncoghlan at gmail.com> a écrit :

On Thu, Jan 24, 2013 at 9:55 PM, Shane Green <shane at umbrellacode.com> wrote: > Not sure if I'm reading the discussion correctly, but it sounds > like there's discussion about whether swallowing CSV values when > confronted with multiple columns by the same name, which seems very > incorrect if so. CSV doesn't even mandate column headers exist at > all, as far as I know. If anything I would think mapping column > positions to header values would make sense, such that > header.items() -> [(0, header1), (1, header2), (2, header3), etc.], > and header1 and header2 could be equal. To work with rows as > dictionaries they can follow the FieldStorage model and have lists > of values–either when there's a collision, or always–so all column > values are contained.

That's not quite the discussion. The discussion is specifically about DictReader, and whether it should: 1. Do any data conditioning by ignoring empty lines and lines of just field delimiters before the header row (consensus seems to be "no") 2. Give an error when encountering a duplicate field name (which will lead to data loss when reading from the file) (consensus seems to be "yes") The problem with the latter suggestion is that it's a backwards incompatible change - code where "use the last column with that name" is the correct behaviour currently works, but would be broken if that situation was declared an error.

It's not really a problem if the new behaviour is conditioned by a constructor argument.

Regards

Antoine.

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